1. Field of the Invention
The present invention relates to a cleaning device to be applied to an image forming apparatus for forming images by an electrophotographic system such as a copying machine, a printer, a facsimile and the like.
2. Description of Related Arts
An image forming apparatus for forming images by an electrophotographic system is provided with, for example, a photosensitive drum. Electrostatic latent image is formed on the surface of the photosensitive drum and then developed by using toner, and subsequently the toner image is transferred on a paper sheet.
After the toner image has been transferred on a paper sheet, the surface of the photosensitive drum is not completely free from toner but usually has residual toner thereon. This residual toner is unnecessary for the next image forming cycle. Therefore, if the residual toner is left as it is, it appears as undesirable blots on the next image, thus causing to lower the image quality.
Therefore, cleaning devices have been adopted for scraping toner remaining on the surface of a photosensitive drum after toner image transferring.
A cleaning device is disposed in a position opposed to the surface of the photosensitive drum after toner image transferring, so as to scrape toner remaining on the surface of the photosensitive drum by rubbing off the same using a fur brush, blade or the like.
If toner leaks through clearances between the cleaning device and the photosensitive drum, the toner stains not only copy sheets but also an optical system, a lamp and the like, thereby causing to lower the copy quality. Therefore, clearances between end faces of a housing for forming a cleaning space, which end faces define an opening opposed to the photosensitive drum surface, and the circumferential surface of the photosensitive drum are generally sealed with a plurality of seals.
Such seals are, for example, side seals (flocked seals) adhered to the housing end faces opposed to both longitudinal ends of the photosensitive drum respectively, and an upstream seal (generally, seal made of a urethane sheet) elongated in the direction of the longitudinal axis of the photosensitive drum and contacting the photosensitive drum on the upstream side of the opening as viewed in the direction of the rotation of the photosensitive drum.
Since the side seals and the upstream seal are adhered in such a manner that they overlap each other at the both longitudinal ends, steps, namely, portions different in level are apt to be formed. If steps are formed, scraped toner is liable to leak from those portions. If, for the purpose of eliminating such steps, the cleaning device is intensely urged against the circumferential surface of the photosensitive drum to absorb the steps by the deformation of the side seals (flocked seals), the upstream seal (urethane seal) is sometimes plucked away by the rotation of photosensitive drum.
Further, each of the side seals comprises a flocked sheet and a seal base, and if steps are provided on the housing end faces of the cleaning device in order to absorb and eliminate the steps formed by the overlapping of the side seals and the upstream seal, the seal base is not in line with the step formed on the housing end face. As a result, it proves that a clink is produced between the step portion on the housing end face and the seal base of each side seal, and disadvantageously, toner leakage through the clink is caused.
Further, especially each side seal (flocked seal) among these seals is intensely urged against the circumferential surface of the photosensitive drum and receives, on the surface thereof, the rotating force of the photosensitive drum. Therefore, whole of each side seal receives a displacing force from the upstream side toward the downstream side as viewed in the direction of the rotation of the photosensitive drum, so that sometimes a portion of the side seal adhered by means of a double-sided tape is displaced or peeled off from the upstream side in the direction of the rotation.
If such displacement or peeling off of the side seal is caused, a clearance is formed between the housing end face of a cleaning unit and the circumferential surface of the photosensitive drum. When the toner in the cleaning space gushes through the clink to stain the inside of the image forming apparatus and an optical system, sometimes it causes problems with the copy quality.
The present invention has been made in the abovementioned background. An object of the present invention is to provide a cleaning device having an excellent sealing ability with respect to the surface of a photosensitive member and capable of preventing recovered toner leakage.
Another object of the present inventions is to provide a cleaning device causing no displacement or peeling off of side seals and thereby capable of preventing recovered toner leakage.
The present invention provides a cleaning device for scraping toner remaining on the surface of a photosensitive member after toner image transferring, having first seals and a second seal adhered to end faces of a housing in such a manner as to partly overlap each other in order to seal the space between the housing end faces and the surface of the photosensitive member. Each first seal includes seal bases and a flocked sheet layered on the seal bases, and a seal base where the second seal overlaps is made smaller in thickness than the other seal base where the second seal does not overlap.
According to the present invention, the first seals and the second seal are adhered to the housing end faces of the cleaning device in such a manner that the first seals and the second seal partly overlap each other. However, since the seal base of the portion of the first seal where the second seal overlaps is made smaller in thickness, no step is formed in the portion where the first seal and the second seal overlap each other.
Further, in another embodiment, a cleaning device according to the present invention includes a seal having a flocked sheet adhered to the housing end face and a pressing member for pressing a part of this seal from the upper surface thereof, and the pressing member is characterized by pressing a portion of the seal abutting on the upstream side of the photosensitive drum as viewed in the direction of the movement of the photosensitive member.
With this structure, when a seal member such as a flocked sheet contacting a photosensitive member and receiving a rotating force of the photosensitive member is adhered, displacement or peeling off of the seal can be completely prevented by pressing the upper portion of the seal by a pressing member from the upstream side as viewed in the direction of the movement of the photosensitive member (the direction of rotating in case of a photosensitive drum). Further, partial curling up of the seal can be prevented, and thereby an adhesive agent used for adhering the seal can be prevented from staining the photosensitive member.
The above-mentioned and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments.